The Document Foundation, the body behind LibreOffice, has announced the availability of LibreOffice 3.6.0 Beta1. The fist beta of the next major version of LibreOffice (aka LO) is intended for evaluation, QA testing, etc. If you are a LibreOffice user and want to help the team in evaluating the upcoming release, you can download it from this link.
However, it's not recommended to use LibreOffice pre-release builds for 'mission-critical' purposes. I don't want to disappoint you but LO 3.6 is not introducing any new UI, as there has been a demand for a it.
Italo Vignoli (The Document Foundation) told me earlier that the team is busy cleaning up the huge pile of code which they inherited from OpenOffice. He said then when the next verison of LO will be announced later this year with a new design, it won't be just the new design, it will be a 'new' LibreOffice. LibreOffice team is also planning to release a mobile version of the popular office suite.